1. Field of the Invention
This invention relates to dual tone multifrequency (DTMF) telephone sets in association with local FCC tariffed telephones lines and more particularly to automatic line control circuitry for use by a subscriber in association with such sets.
2. Description of the Prior Art
Tone dialing DTMF telephone sets include a keypad matrix dialer for controlling the generation of dual tones of the FCC tariffed line by depression of a tone key of a 4.times.3 key pad matrix. Usually four different low frequency tones (from 697 to 941 hz) can be generated by depressing two buttons simultaneously in each of the matrix rows and three different high frequency tones (from 1209 to 1477 hz) can be generated by depressing two buttons simulaneously in each of the matrix columns. Such single tones are within the voice band of the FCC tariffed local line.
Long-distance auto dialing has been described using simultaneous depression of two buttons of the key pad matrix of a DTMF telephone set to initiate and control operations. In U.S. Pat. No. 4,506,116 for "Security Dialing System for Long Distance Telephone Systems", L. J. Genest, issued May 19, 1985), a 1477 hertz tone is generated by depressing the "#" and "9" buttons of a DTMF telephone. As the telephone line is monitored, the tone is detected by a phase locked loop locked at 1477 hertz. A processor then controls a tone generator to automatically transmit the telephone number of a long-distance service on the telephone line by retrieving and executing the stored telephone number from the memory of the processor. A second 1477 hertz tone is used to identify the user's billing code, which is also stored in memory, to more quickly access the long distance telephone service. After the telephone number of the long-distance service and after the user's billing code have been auto dialed, the subscriber still must hand-dial the desired long-distance number. However, such a prior system uses but a single frequency and has minimum flexibility.
While the need to increase the memory size of auto dialers attached to a subscriber's telephone has been recognized, such dialers often require special circuitry or equipment. Also, installation may require modifications beyond the capability of the home user. In U.S. Pat. No. 4,011,414 for "Automatic Dial System For a Subscriber Telephone", W. D. Warren, an auto dialer is described that uses a mechanical switcher to initiate encoding of numbers from a button dialer to the memory of a microprocessor. The microprocessor along with special hardware are stored in a specialized compartment below the dialer. While the button dialer can be mounted on a standard telephone base, the electrical and mechanical connections may be a problem since many different telephone base constructions are presently available.
Increasing the number of functions that can be provided to the subscriber's home telephone set has also been recognized. In U.S. Pat. No. 4,459,434 for "Home Telephone Exchange", G. G. Benning et al, special service circuits are connected to the unused conductors (B and Y) of a quad telephone line and then enabled using command signals on the remaining tip and ring conductors. In that way, chime or other special rings, intercom messaging, voice paging, etc., are provided. A special controller is connected in series in the telephone line before connection with its usual cable connector. In one instance when the ringer of the set is enabled, the subscriber's in-premises line is first disabled. Then a local battery is applied to the in-premises line. Special ringers can be activated that bypass the usual ringers of each telephone set. When the subscriber answers the ring by placing the telephone set off-hook, the controller reestablishes contact by monitoring loop DC current after disconnecting the tone generator and local battery from the line. In another instance, a hold function is established by a series of off-hook signals. After insertion of a terminating resistor up-line for maintaining an off-hook condition, the in-premises tip and ring lines are disabled. Further flashing of off-hook signals reverses the procedure. In yet another instance, off-hook flashes followed by a dual tone or rotary dial pulse (not in the audio range) are used to activate special circuits that can include an amplifier in series with a microphone for voice paging, through a special signaling circuit. A DTMF circuit is used to recognize the dual tones, while a loop current detector detects the rotary tone pulse. After the CPU of a microcomputer disables the in-premises line based on the off-hook DC flashes, the nonaudio tones are used to control the CPU. Commands of the CPU activate the service circuit. But a separate special signaling circuit must be used since the service circuit must be enabled through the B and Y leads. In yet another instance, the controller is placed in parallel with the in-premises line but each service circuit and telephone set is provided a separate switching network. Commands to the special circuits still pass via the B and Y lines. Hence a special signaling circuit is still a requirement to selectively disable and enable such elements relative to the in-premises line.
The above-mentioned modifications may be beyond a subscriber's installation capability, especially where such modifications must be connected in up-line from the subscriber's in-premises mating connector. The circuits themselves may adversely affect usual telephone operations. For example, line disconnects by in-premise electro-mechanical switches are not encouraged on FCC tariffed lines. Line load can vary. Voltage spikes can also occur and be passed up-line to the central office and its switching equipment. Introducing an in-premises d.c. voltage source may not be compatible with operating requirements of existing equipment. Special signal circuits for the B and Y lines further complicate proposed operations, as where a quad line is unavailable, or where the B and Y leads are already in use for another purpose, such as a secondary line. Speed dialing is not inherent in such circuitry; the subscriber must still purchase a separate speed dialer.
Prior art memory-dialers were used in series, either one dialer per telephone, between each telephone set and its wall jack, or, one dialer per telephone line, between all telephones and the telephone company line. Series connection was required to isolate the telephone from the telephone company line, since any tone-dialing telephone push-button used in the usual way to operate the dialer would also trigger telephone company systems. There are two general prior art solutions to this problem.
The first method requires that the memory dialer have its own separate keyboard to store or recall numbers. This eliminates any possible interference with the telephone company equipment, since the keyboard signals do not appear on the telephone line. In addition, simple parallel hookup is possible. The disadvantage, however, is that the memory dialer can only be operated from the single location where it is located, leading to a requirement for one dialer per telephone.
The second method requires that the memory dialer be designed with two isolated "halves" which can be connected internally and automatically, at appropriate times. The two "halves" of the dialer are connected between the telephone and the telephone company using a four-wire series hookup, so that the telephone pushbuttons can be used in isolation in the usual way to cause the "telephone company side" of the device to select and dial a previously stored number. After dialing, the "customer side" of the device is connected to the "telephone company side" by an internal "pass-thru" connection. With this method, it is possible to provide memory dialing on all telephones, but only if the dialer is installed between the telephone company line and all telephones using the inconvenient "series" method of connection.
Thus no prior art method exists for providing memory dialing for all telephones on one telephone line, with one device using simple "parallel" connections.
Some functions were available in the prior art via separate devices. Prior art "whole-house" memory dialers require "series" connection, as described previously. Prior art "hold" devices after offer parallel connection, but not other features except "hold". An alarm clock could be used as a reminder to place a call, but it would not dial the call automatically. A timer could be used to time the length of calls but it would not start automatically when the user picks up the telephone or reset automatically when the user hangs up the telephone receiver. Paging systems using buzzers, chimes, etc., are available but do not use the existing telephone wiring and thus require their own separate wiring system.
As described previously, providing automatic dialing for every telephone on one line requires either inconvenient series connection between the telephones and the telephone company, or, one memory dialer per telephone connected in series with each telephone. Prior art memory dialers do not provide conversion of all tone-dialing telephones on one telephone line to memory dialing with a simple parallel connection to one telephone jack.
Additionally, no known device currently available offers all of the features available in this one invention by any other method, evey by using an unwieldy assortment of various devices.